U.S. Pat. No. 5,232,458 entitled "Safety Syringe with Retractable Self-biased Needle" issued to the same inventor of this application disclosed a needle secured in a plug 13 embedded in a front portion of the syringe having a needle head portion formed on a rear portion of the needle and a plunger slidably held in the syringe having a biasing socket recessed in a front portion of the plunger engageable with the needle head portion for biasing the needle obliquely within the syringe when retracting the plunger and the needle into the syringe, thereby preventing an outward protruding of the retracted needle for preventing its injury to the surroundings.
However, the plug 13 should be provided in a front portion of the syringe for holding the needle 2 in the plug 13 to be normally positioned at a front portion of the syringe 1 for injection use.
In order to save material cost and enhance assembly convenience of such a safety syringe, the plug 13 is expected to be eliminated or omitted, and the needle 2 would then be directly secured at a front portion of the syringe 1 for simplifying its production and decreasing its cost.